Horizontal deflection apparatus for a flat two-color picture tube



July 30, 1968 H, FREESTONE ET AL 3,395,312

HORIZONTAL DEFLECTION APPARATUS FOR A FLAT TWO COLOR PI CTURE TUBE Filed Dec. 17, 1964 4 (205 IQIUUJKNQ JQLIONPQOI mvsmoas: HARRY T. FREESTONE, svsuo E. HAVN,

THEIR ATTORNEY.

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3,35,312 HORIZONTAL DEFLECTION APPARATUS FOR A FLAT TWO-COLOR PICTURE TUBE Harry T. Freestone, Paoli, Pa., and Svend E. Havn, Liverpool, N.Y., assignors to General Electric Company, a

corporation of New York Filed Dec. 17, 1964, Ser. No. 419,134 7 Claims. (Cl. 315-27) ABSTRACT OF THE DISCLOSURE A flat two-color picture tube comprising a pair of electron guns mutually parallel and parallel to a target lying in a plane equidistant from the guns. The beam from each of the guns is directed through separate static and dynamic horizontal deflection magnetic fields. The static magnetic fields are established by a magnet, pole plates, and ferromagnetic member forming a magnetic circuit with a flux path common to each of the static fields. The dynamic fields are established by a yoke, coils wound around the yoke, and a ferromagnetic member forming a magnetic girlcuit with a flux path common to each of the dynamic e ds.

This invention relates to a flat two-color television picture tube, and more particularly to apparatus for controlling the horizontal deflection of the electron beam in such a tube.

The most common types of color television picture tubes have employed a plurality of electron guns to deliver the necessary tone and hue information. A problem inherent in the use of a plurality of electron guns is that of registering the electron beams. This is to say that the point and time of impingement of each beam on the target must be precisely coordinated. In the flat color picture tube in which this invention is embodied, a two-color system is utilized, requiring a pair of electron guns to convey the necessary tone and hue information. The guns are disposed mutually parallel and parallel to a common, twofaced target disposed in a plane equidistant between the guns. With this arrangement the registration problem presents itself as a requirement that the electron beam impinging on one side of the target be in exact registration with the electron beam impinging upon the other side of the target.

Accordingly, it is an object of this invention to provide a flat two-color television picture tube having horizontal deflection apparatus which etfects a precise registration of the electron beams along the horizontal dimension of the target.

Further objects and advantages of our invention will become apparent as the following description proceeds. The subject matter which constitutes our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the object of this invention, in one form thereof, we provide a flat two-color picture tube having a pair of electron guns arranged mutually parallel and parallel to a target disposed on a plane equidistant between the guns. The beam from each gun is influenced initially by horizontal deflection fields comprising a dynamic magnetic field and a static magnetic field. The horizontal registration of the beams impinging on opposed faces of the target is accomplished by providing that the same magnetic flux operate on each beam. The flux common to both dynamic magnetic fields is established by a deflection yoke outside the tube envelope. Similarly, the flux common to both static magnetic fields is established by a permanent magnet outside the tube. Disposed in each of the magnetic circuits, between the electron beams, are ferromagnetic States Patent ice members which serve to substantially reduce the reluctance in the circuits and to shape identical fields for each beam. Thus, the dynamic and static magnetic fields acting on each electron beam, being identical, will deflect each beam equally and effect a registration of the beams along the horizontal dimension of the target.

For a better understanding of our invention, reference may be made to the accompanying drawings in which:

FIGURE 1 is a side elevation view of the picture tube with a portion of the tube envelope broken away,

FIGURE 2 is a sectional view taken on lines 22 in FIGURE 1,

FIGURE 3 is a bottom view of the picture tube.

Referring to the drawings, and particularly to FIGURE 2, it will be seen that we provide a television picture tube of the flat type. The tube comprises a transparent glass envelope 1 enclosing a vertically disposed target 2 having a left face 3 and a right face 4 (as seen in FIGURE 2). Each of the opposed faces 3, 4 of the target 2 is coated with a layer of phosphor material, the layer 5 on the left face 3 being capable of emitting a first color, and the layer 6 on the right face 4 being capable of emitting light of a second color. A transparent coating 7 of electron permeable metal covers each phosphor layer, the coatings serving to maintain a constant potential on the target 2 during operation of the tube.

A pair of electron guns, a left 8 and a right 9, are arranged with their axes mutually parallel and parallel to the target 2. The left gun 8 projects an electron beam 10 adjacent the left face 3 of the target 2 and the right gun 9 projects a beam 11 adjacent the right face 4 of the target 2.

In order that the electron beams 10, 11 can be made to scan the respective faces 3, 4 of the target 2 in the vertical dimension, two sets of vertical deflection apparatus are provided. The vertical deflection apparatus associated with each face of the target 2 is identical and, forming no part of this invention, it has been illustrated in accordance with the teachings of Patent 3,118,084, assigned to the assignee of this invention. Referring to FIGURE 2, the apparatus associated with the left face 3 of the target 2, for example, comprises an electrically resistive coating 12 on the inside surface of the side wall 13 and top 14 of the envelope 1, an electrically conductive coating 15 on a lower portion of the side wall 13, and an electrically conductive coating 16 on a parabolic support member 17 extending from the target 2. A conductor 18 in the upper left hand corner of the tube is connected to the resistive coating 12, and is grounded through resistor 19. A source of vertical deflection voltage 20 producing a signal having a suitable wave form (shown at 21) is connected by means of lead 22 to the conductive coating 15 at the lower extremity of resistive coating 12.

For purposes of illustration assume that a voltage of 10 kilovolts is applied to the target 2 and the conductive coating 16 on the parabolic support member 17, and that a maximum of 8 kilovolts is generated at the peak of the signal 21 applied by the variable source 20. Note that the resistive coating 12 on the side Wall 13 and the resistor 19 act as a voltage divider and also that an electric field gradient, increased in intensity in the direction from the lead 22 to the conductor 18, is established, An electron beam projected into the space adjacent the face 3 of the target 2 will be attracted to the target 2 by a force proportional to the electric field established between the target 2 and the resistive coating 15 on the side wall 13 of the tube. Thus, by applying the signal from the source 20 to the coating 15, a varying field will be established in the space adjacent the target 2 and the electron beam 10 will vertically scan the target 2. The effect of the voltage 3 gradient established by the use of the resistive coating concerns the invention set forth in the referent patent and is fully explained therein.

Our invention is concerned with the apparatus for deflecting and registering the electron beams 10, 11 along the horizontal dimension of the target. As each of the beams 10, 11 is projected from its gun, it is first subjected to a dynamic magnetic field which deflects the beam, by the well-known principles of electron optics, along the horizontal dimension of the target 2. -In order to then collimate the beams in vertical paths in a vertical plane preparatory to being acted upon by the vertical deflection apparatus, a static magnetic field is established in the path of each beam.

In the past it has been a problem to create identical fields acting upon the beams 10, 11 so that each beam will experience an exactly equal deflection and will impinge in registration on the opposed faces 3, 4 of the target 2. Our invention has solved this problem by providing that the same magnetic flux operate on each beam. In other words, the varying magnetic fields acting on :the beams 10, 11 form portions of a first magnetic circuit, and, likewise, the static magnetic fields acting on the beams 10, 11 form portions of a second magnetic circuit.

Translated into structure, the dynamic magnetic fields are established in a magnetic circuit through a deflection yoke 23, the poles 24 of which embrace a lower portion of the envelope 1 forward of the electron guns 8, 9. The circuit is established through the yoke 23 by a coil 25 energized by a source 26 delivering a signal of suitable wave form (shown at 27).

In order to shape the dynamic magnetic fields and appreciably reduce the reluctance in the magnetic circuit, a linear member 28, formed from a ferromagnetic material, is disposed within the envelope 1 between the beams 10, 11 and in line with the poles 24 of the yoke 23. The member 28 is located centrally between the beams 10, 11 in order that the air gaps at the ends thereof, in which the dynamic magnetic fields are established, will be identical. It is evident that with this arrangement a single magnetic circuit establishes fields of identical shape and intensity operating on each of the electron beams 10, 11. Thus, the beams projected into the dynamic magnetic fields will each be deflected along the horioznt-al dimension of the target 2 with an identical force.

In order that the electron beams deflected by the varying magnetic fields will be then collimated in vertical paths in a plane parallel to the target 2, we provide a linear permanent magnet 30 having magnetically soft pole plates 31 extending adjacent the outer surfaces of the opposed side walls of the envelope 1. The pole plates 31 are so shaped that electrons leaving the dynamic fields and entering the static fields established between the pole plates 31 will be deflected vertically upwardly in a plane parallel to the target 2. A second ferromagnetic member 32, similar in shape to the pole plates 31, is supported within the envelope 1 between the electron beams 10, 11 and aligned with the plates 31. The member 32, like the ferromagnetic member 28, is located centrally between the beams 10, 11 in order that the air gaps adjacent its ends, in which the static magnetic fields are established, will be identical. The member 32 functions as does the ferromagnetic member 28 to shape the static magnetic fields established between the poles 31 of the permanent magnet 29 and to reduce the reluctance in this magnetic circuit. Thus, as with the dynamic magnetic fields, the static magnetic field acting on each of the electron beams is identical in shape and intensity because each field is established in the same magnetic circuit.

The ferromagnetic members 28, 32 have been illustrated as having a uniform cross-section in the dimension transverse to the target 2; however, members of other suitable configurations could be employed. For example, the members 28, 32 might comprise end plates joined by a connecting bar or bars of great enough cross-sectional area to carry the total flux without saturating.

A shield 33 and a conductive lining 34 on the inner surface of the envelope 1 in the region of the horizontal deflection portion of the tube are maintained at the same potential to isolate the horizontal deflection portion from the effects of high intensity electric fields generated by the vertical deflection apparatus. I

In summary, as the electron beams pass through the identical dynamic fields and identical static fields, each experiences an equal deflection. It is evident then that, so long as the vertical deflection apparatus associated with each face of the target is made identical, and this is entirely feasible, the beams will impinge in registration on the opposed faces of the target. Thus, the excited phosphors on each face will also be in exact registration to form an image with an undistorted hue.

Our invention is not limited to the particular details of the construction of the embodiment illustrated and we contemplate that various and other modifications and applications will occur to those skilled in the art. It is therefore our intention that the appended claims shall cover such modifications and applications as do not depart from the true spirit and scope of our invention.

What We claim as new and desire to secure by Letters Patent of the United States is:

1. In a cathode ray tube,

(A) a target having a first face and an opposed second face,

(B) 'a first electron beam source projecting a first beam adjacent said first face,

(C) a second electron beam source projecting a second beam adjacent said second face, and

(D) means establishing a magnetic circuit through the tube,

(B) said circuit including identical fields comprising flux, substantially all of the flux being common to each of said fields, said fields lying in the paths of each of said beams and acting equally on said beams to effect registration of said beams along one dimension of said target.

2. The cathode ray tube defined in claim 1 wherein said fields are dynamic.

3. The cathode ray tube defined in claim 1 wherein said fields are static.

4. In a cathode ray tube,

(A) a target having a first face and an opposed second face,

(B) a first electron beam source projecting a first beam adjacent said first face,

(C) a second electron beam source projecting a second beam adjacent said second face, and

(D) first means establishing a first magnetic circuit through the tube, said first circuit including identical dynamic fields comprising flux, substantially all of the flux being common to each of said fields, said fields lying in the paths of each of said beams and serving to deflect said beams along one dimension of said target,

(E) second means establishing a second magnetic circuit through the tube, said second circuit including identical static fields comprising flux, substantially all of the flux being common to each of said fields, said fields lying in the paths of each of said beams and serving to collimate said beams,

(F) said dynamic fields and said static fields acting equally on said beams to effect registration of said beams along said one dimension of said target.

5. The cathode ray tube defined in claim 4 wherein said first means comprises a ferromagnetic yoke embracing a portion of each of said beams, a coil on saidyoke, and signal generating means connected to said coil, and wherein said second means comprises a permanent magnet having parallel pole plates embracing another por: tion of each of said beams.

6. In a cathode ray tube:

(A) a target having a first face and an opposed second face,

(B) a first electron beam source projecting a first beam adjacent said first face,

(C) a second electron beam source projecting a second beam adjacent said second face, and

(D) first means establishing a first magnetic circuit through the tube, said first circuit including identical dynamic fields in the paths of each of said beams, said fields serving to deflect said beams along one dimension of said target,

(E) a first ferromagnetic member disposed in said first magnetic circuit centrally between said beams, said member serving to shape said dynamic fields and to reduce the reluctance in said first magnetic circuit,

(F) second means esetablishing a second magnetic circuit through the tube, said second circuit including identical static fields in the paths of each of said beams, said static fields serving to collimate said beams,

(G) a second ferromagnetic member disposed in said second magnetic circuit centrally between said beams, said second member serving to shape said static fields and to reduce the reluctance in said second magnetic circuit,

(H) said dynamic fields and said static fields acting equally on said beams to effect registration of said beams along said one dimension of said target.

7. In a cathode ray tube having an envelope:

(A) a target having a first face and an opposed second face,

(B) a first electron beam source projecting a first beam adjacent said first face,

(C) a second electron beam source projecting a second beam adjacent said second face, and

(D) first means establishing a first magnetic circuit through the tube, said first circuit including identical dynamic fields in the paths of each of said beams, said fields serving to deflect said beams along one dimension of said target,

(E) said first means comprising a ferromagnetic yoke outside said envelope embracing a portion of each of said beams, a coil on said yoke, and a signalgenerating means connected to said coil,

(F) a first ferromagnetic member disposed in said first magnetic circuit centrally between said beams, said member serving to shape said dynamic fields and to reduce the reluctance in said first magnetic circuit,

(G) second means establishing a second magnetic circuit through the tube, said second circuit including identical static fields in the paths of each of said beams, said static fields serving to collimate said beams,

(H) said second means comprising a permanent magnet having parallel pole plates outside said envelope embracing another portion of each of said beams, and

(I) a second ferromagnetic member disposed in said second magnetic circuit centrally between said beams, said second member serving to shape said static fields and to reduce the reluctance in said second magnetic circuit,

(J) said dynamic fields and said static fields acting equally on said beams to effect registration of said beams along said one dimension of said target.

References Cited UNITED STATES PATENTS 2,580,355 12/1951 Lempert 315-18 2,978,601 4/1961 Aiken 313-92 3,313,970 4/1967 Aiken 313-79 ROBERT L. GRIFFIN, Primary Examiner. R. BLUM, Assistant Examiner. 

